The market preference for set top boxes and the like (such as computers, game consoles, DVD players, CD players, etc.) is to have such devices be small, compact, and versatile. However, such preferences increasingly challenge the designers, because set top boxes and the like are required to perform more functions, which require more internal components. This results in more challenges to appropriately manage the heat generated by some of these components in these crowded devices, which is potentially detrimental to the device's longevity and performance. This crowding also results in more challenges to appropriately shield some components from the risk of electrostatic discharge and/or from interference (such as from radiofrequency interference) to and from other components and external sources.
To appropriately guard at-risk components, the common closed polygon vertical wall metal structures (i.e. shields) have been employed, which are secured generally to a printed circuit board. However, the devices that employ such shields tend to be items that are mass produced. As such, the shields in high volume production environments require rapid processing that requires the need for inspection of the mounted components contained within the shields. Thus, the shields and shield covers must be applied in these high volume production environments in a fast and reliable manner and the shield covers need to be easily removable for inspection and possible reworking of components contained therein.
FIG. 1 and FIG. 2 show an electronic device 1 and single height shield assembly 50 within the electronic device 1, respectively, to which the current principles are applicable. FIG. 1 more specifically shows the electronic device having a front wall 2, rear wall 3, top 4, and side walls 6. The electronic device 1 can be a set top box or the like (such as computers, game consoles, DVD players, CD players, etc.) that further includes a panel jack 5 for connecting cables 9, wherein one of the electrical connectors can be an F-connector 12 or the like. This view with the plurality of cables 9 connected to the electrical connectors on the panel jack 5 is indicative of how crowded the components within the electronic device 1 can be. As such, electronic devices 1 which can have a tuner or the like will require the shield assembly. In this view, one of the electrical connectors on the panel jack 5 can be an F-connector 12 or some other connector 13 that can be connected to some internal component requiring shielding.
In crowded devices, the F-connectors are required to be located in close proximity to other components on the printed circuit board and each of these components themselves can require shielding. However, the shielding requirements for the different components can be uniquely different. In such cases, some have employed multiple shields. While others have employed a shield assembly 50 such as that shown in FIG. 2 in which the height of the entire shield assembly, which can be a tuner shield assembly, is made at one large or full height in an effort appropriately shield all of the vulnerable components contained therein. Here, the use of F-connectors 12 often dictates the height of the shielding for all of the components in the region. This view shows that the shield assembly 50 includes a shield 51 having vertical walls and a shield cover 63 that covers the components captured within each of the shield rooms made by the vertical walls. In fact, the high vertical walls have been found to be quite beneficial to their intended shielding purpose. FIG. 2 further shows spring tabs or attachment springs 62 of the shield cover 63 that engage ridges or indents 64 on the vertical walls of the shield 51.
FIG. 3B shows a plan front view of previous spring tabs or attachment springs 62 of the shield cover 63 and FIG. 3A shows a cross section view of the spring tabs or attachment springs 62 cut along slice A-A in FIG. 3B. The spring tabs or attachment springs 62 can have edges 35 that bend inward and then outward as they extend from the top cover to create grasping portion 37 which extend over ribs or indents 64 in the vertical peripheral walls to secure the top cover to the shield. The spring tabs or attachment springs 62 can be flexible and the design of the spring tabs or attachment springs 62 can be such that a gap 69 exists between the interior upper vertical portion of the spring tabs or attachment springs 62 and the corresponding exterior upper vertical portion of the shield wall. Such a gap 69 can be advantageous in that it provides some manufacturing tolerance for cover formation and it permits the cover 63 to be placed on and removed from the shield 51 without the need for significant force.
FIG. 4B shows a plan front view of another previous spring tabs or attachment springs 62 of the shield cover 63 and FIG. 4A shows a cross section view of the spring tabs or attachment springs 62 cut along slice A-A in FIG. 4B. In this design, a gasket or extra shielding 61 is placed in the gap 69 to prevent possible radiofrequency (RF) interference around the gap 69 shown in FIG. 3A. However, it has been recognized that gaskets or extra shield material adds cost and makes the shield cover 63 more difficult to apply and remove.
It should be noted that radiofrequency shielding for many devices must meet mandatory emission specifications during testing. In fact, it has been the case that at times when a shield cover/lid does not meet electromagnetic interference emission specifications, the failure causes the designer to engineer to make changes in the design of the shield and/or develop and employ additional parts such as a gasket in order to have the shield pass tests that show conformance with emission specifications. Unfortunately, as mentioned above, adding extra material such as a gasket can make the application and removal of a shield cover difficult because there is extra friction and more contact area. However, if the cover/lid is designed to not have a tight fit by designing an oversized gasket or other part, there can be direct path for electromagnetic interference (EMI). Additionally, it follows that awareness of the possibility of such gaps can cause the manufacturer to apply greater force in the application of the shield cover than desirable, thereby providing the possibility of damaging the shield, the printed circuit board which supports the shield and components in the vicinity. Additionally, to resolve this gap issue in the past, designers have at times adjusted the spring tabs to ensure tight fit.
In light of the above mentioned shortcomings of the previous RF shield assemblies 50, a need exists for a new RF shielding assembly that provides for superior RF shielding and yet permits the shield cover to be applied and removed easily.